Precipiton Reagents:  Precipiton Phosphines for Solution-Phase Reductions

Abstract

[structure: see text] [structure: see text] [structure: see text] Several Precipiton phosphines were prepared and employed in the Staudinger reaction and in the reduction of secondary ozonides. Both amines and aldehdyes were obtained in good to excellent yields and purities. After use of the phosphine, isomerization and precipitation of the spent phosphorus reagent were induced by exposure to visible light in the presence of erythrosin B, a triplet sensitizer. Products were isolated by simple filtration. The use of the triplet sensitizer has the added advantage of eliminating [2 + 2] cycloaddition reactions between trans-Precipitons.

Naphthyridine tetramer with a pre-organized structure for 1:1 binding to a CGG/CGG sequence

“…The ( Z )-stilbene linker in Z -NCTS was designed to place the naphthyridines in preorganized positions appropriate for the binding. Synthesis of NCT (22) and Z -NCTS was achieved by reductive amination of glutaraldehyde and ( Z )-4,4′-diformylstilbene (47), respectively, with the secondary amino group of NCD (Scheme 1). NCTB and E -NCTS were synthesized from 3,3′-bis(bromomethyl)biphenyl (48) and ( E )−4,4′-bis(bromomethyl)stilbene (49) using a nucleophilic substitution reaction with two NCD molecules.…”

“…To a solution of NCD (171 mg, 0.34 mmol) and ( Z )−4,4’-diformylstilbene (47) (35 mg, 0.15 mmol) in CHCl 3 (1.5 ml) and MeOH (9.2 ml) was added acetic acid (27 µl, 0.47 mmol) to adjust the pH at 6, and the reaction mixture was stirred at ambient temperature for 10 min. To this solution was added NaBH 3 CN (21 mg, 0.33 mmol) dissolved in MeOH.…”

Observing Second‐Order Nonlinear Optical Properties by Symmetry Breaking in Centrosymmetric Furan‐Containing Oligoaryl Cyclophandienes

“…176-178 8C; IR (KBr): ñ = 3032, 2958,2931,2862,1617,1509,1492,1466,1425,1104,936,846 22.7, 25.9, 32.0, 37.7, 37.9, 108.4, 123.2, 123.3, 124.8, 129.0, 129.2, 129.9, 136.8, 137.1, 147.3, 151.5 (19.47 g, 60.8 mmol) in THF (300 mL) at À78 8C. After the reaction mixture had been stirred at À78 8C for 50 min, a solution of 4,4'-diformyl-Z-stilbene [23] (5.0 g, 21.4 mmol) in THF (100 mL) was added at À78 8C. The mixture was stirred for an additional 1 h at À78 8C, and then gradually warmed to RT.…”

Redox‐Switchable Phase Tags – Facile Mitsunobu Reactions using Ferrocenyl‐Tagged Triphenylphosphine

“…Infamous in this respect are reactions in which triphenylphosphine is used as a stoichiometric reagent [2] such as the Mitsunobu [3] and the Staudinger reactions [4] or the reduction of primary ozonides. [5] Nonetheless, the Mitsunobu reaction is a powerful synthetic tool for the condensation of an acidic pronucleophile (RXH) and an alcohol (R'OH), due to its wide applicability, stereospecificity and mild reaction conditions. Several strategies have been developed to deal with purification problems in the Mitsunobu reaction such as polymer-supported reagents, [6] basic phosphines, [7] tagged phosphines, various azodicarboxylate reagents, [8,9] fluorous reagents, [10] or phase switching approaches, [11] as described in detail in a recent review by Dandapani and Curran, dealing exclusively with Mitsunobu purification strategies.…”